1. Field of the Invention
The present invention relates to a water treating method including irradiating a water with a laser beam so as to form a denatured layer in the inside of the water, and thereby to separate the wafer into a back-side wafer and a face-side wafer.
2. Description of the Related Art
Devices such as ICs and LSIs utilized for various electronic apparatuses are manufactured by slicing a semiconductor ingot such as a silicon ingot to form wafers each of which serves as a base for the devices, grinding both sides of the wafer and polishing a surface of the wafer to mirror finish the surface, and fabricating circuits at the mirror-finished surface (refer to, for example, Japanese Patent Laid-open No. 2006-100786 and Japanese Patent Laid-open No. 2005-317846).
In the process of manufacturing the devices starting from the semiconductor ingot, however, most part of the semiconductor is discarded, which is extremely uneconomical. Specifically, it is known that let the volume of the semiconductor ingot be 100%, then the volume discarded during the step of slicing the semiconductor ingot to form wafers used as bases is 20%, the volume discarded during the step of mirror finishing the surface of the wafers is 20%, the volume discarded during the process in which the back side of the wafer provided with devices is ground to thin the wafer is 55%, and the volume discarded during the step of dicing the wafer into the individual devices is 1%. Thus, 96% of the silicon ingot is discarded, as is known.